Age related declines in speech recognition are common for older adults and pose serious consequences for quality of life, which include a variety of poorer health outcomes and decreased economic productivity. Current rehabilitation methods largely depend on amplification to restore speech information and improve speech recognition. However, age-related changes throughout the central and peripheral auditory system may limit the efficacy of intervention strategies and contribute to speech recognition difficulties in older adults. Despite the growing importance of understanding the effects of age on the central auditory system and speech recognition difficulties, studies linking these related phenomena in humans are scarce. The proposed projects use complementary neuroimaging and behavioral methods to identify the structural and metabolic bases for neural declines that impact speech recognition with age. The experiments in Aim 1 examine how age-related deficits in the auditory nerve contribute to dyssynchrony and lead to changes in neural function, structure, and metabolism throughout the central auditory system, and declines in speech recognition. The experiments in Aim 2 characterize how advanced age alters cortical microstructure and contributes to slowed neural processing speed, which is predicted to limit speech envelope encoding and result in poorer speech recognition. By identifying specific neural deficits that contribute to age-related speech recognition declines, the proposed project may lead to improved and more individualized diagnoses and detection of specific age-related auditory processing deficits, and guide the development of more personalized signal processing algorithms for amplification devices and neural based interventions.